The goal of the proposed research is to develop better definitions of childhood overweight and obesity based on the association of childhood weight with health consequences in adulthood. Current definitions are based on a child having a value above an arbitrary cut-off in a distribution of weight or body mass index (BMI; kg/m2). Children in the US and worldwide are becoming excessively heavy at progressively younger ages. Therefore, it is both critical and timely that we examine the risks of excess weight and weight change in childhood for adult disease and create evidence based cut-offs. We will use data from the Copenhagen School Health Records Register, which is based on a population of school children born between 1930 - 1983 and contains computerized weight and height measurements on 351,777 boys and girls in the Copenhagen area. We will use survival analysis techniques to examine if childhood BMI and change in BMI from age 7-14 y is associated with an-increased risk of developing heart disease, cerebrovascular disease, obesity-related cancers and mortality in adulthood. Based on the association of childhood BMI with adult disease and mortality, we will develop criteria to define categories of childhood overweight and obesity.